Anti-cornering protection for railroad classification yards



Nov. 24, 1970 G. F. MCGLUMPHY ET AL 3,543,020

ANTI-CORNERING PROTECTION FOR RAILROAD CLASSIFICATION YARDS Filed March13, 1968 am 2 Car! l O O O C Q O F BY Unaw/ond 7. Sa DZQS.

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THEE? HTWOAJVF/ United States Patent ANTI-CORNERING PROTECTION FORRAILROAD CLASSIFICATION YARDS George F. McGlumphy, Wilkins Township,Allegheny County, and Crawford E. Staples, Edgewood, Pa., assignors toWestinghouse Air Brake Company, Swissvale, Pa., a corporation ofPennsylvania Filed Mar. 13, 1968, Ser. No. 712,739 Int. Cl. B611 7/08U.S. Cl. 246-1 10 Claims ABSTRACT OF THE DISCLOSURE As a cut traverses aswitch in a classification yard, a time interval is computed as aproduct of the distance to clearance beyond that switch and thedifference between the reciprocals of the speeds of that cut and thefollowing cut, where the following cut speed is greater. During thistime interval, delivery of a diverging route switch control for thefollowing cut is delayed. If the following cut enters the switchdetector section prior to expiration of computed time delay, the switchis locked to prevent a diverging movement which would result in acornering accident.

This invention pertains to a method of and apparatus for preventing thecornering of cuts of cars in railroad classification yards. Morespecifically, our invention relates to an arrangement which enforces acomputed time delay prior to the establishment of diverging routes overa track switch if relative speeds of successive cuts of cars which areto move over that switch create the probability of a corneringsituation.

One problem in the operation of railroad classification yards, for whichno satisfactory solution has been achieved in the past, is corneringbetween successive cuts of cars moving over a particular switch alongdiverging routes. The term cornering is herein defined as that conditionor action which occurs when a second cut of cars, moving over a trackswitch along the diverging route, catches up with the preceding outwithin the distance beyond the switch where there is no clearancebetween the bodies of the railroad cars and a collision occurs. Underthis condition, serious damage to the cars and their contents may occurand the possible derailment of the cars causes extra expense and delaysthe scheduled operations of that particular yard. As partial solutionsin the prior systems used to control such classification yards, a firstmethod reduces the humping speed and thus increases the separationbetween successive cuts of cars while a second solution provides longerswitch detector sections so that the switches will be locked in positionwhen successive cuts of cars have relatively little separation. Thefirst solution reduces the operating capacity of the yard since a fewernumber of cars may be'moved over the hump in a specific period of time.The second solution tends to increase the frequency of misrouting ofcuts of cars and thus slows yard operations and increases the expensesince time must be expended to find the cars which have been misroutedand then trimming time allowed to correctly reclassify or position thecars in the storage tracks. However, the cornering problem is seriousenough that the delays or reduced capacity caused by these two partialsolutions received some acceptance since the collisions and possiblederailments when cornering occurs are more than likely to cause evenmore expense and serious delays. Further, it is recognized that afollowing cut of cars which is moving at a higher speed and catches upto a preceding cut moving along the same track so that coupling occursduring movement causes no more dam age, in fact is no more serious, thancoupling occurring in the storage tracks. With the use of digitalcomputers in the more recent and improved automatic control systems forclassification yards, there is an increased capacity for handlingcontrol functions due to the capacity of the computer. An example ofsuch a system is described in the Automatic Classification Yard SystemManual 555 published by the Signal & Communications Division ofWestinghouse Air Brake Company, the assignee of this presentapplication. This increased capacity of the control system to handleadditional functions and information has suggested to us a new andimproved solution for the problem of cornering between successive cutsof cars traversing the same switch.

Accordingly, an object of our invention is an improved arrangement foranti-cornering protection in railroad classification yards.

Another object of our invention is apparatus which prevents corneringaccidents between successive cuts of cars moving across a track switchwhen the diverging route has been preselected for the following car.

Still another object of our invention is an improved method forproviding anti-cornering protection during the automatic operation ofrailroad classification yards.

A further object of our invention is a method for providinganti-cornering protection at a track switch in which the operation ofthis switch to establish a diverging route for the second of twosuccessive cuts of cars traversing the switch is delayed for a timeinterval computed in accordance with the car clearance distances beyondthe switch and the difference in speeds of the two cuts.

It is also an object of our invention to provide an anticorneringarrangement which computes a time delay for enforcement prior to theoperation of a switch to establish a diverging route for the second oftwo successive cuts of cars moving across the switch if a probability ofthe cornering of the lead out of cars by the following cut exists.

Other objects, features, and advantages of our invention will becomeapparent from the following description when taken with the appendedclaims.

In the practice of our invention, it is apparent that the principalapplication of the novel arrangement will be in classification yardswhere the operation is fully automated through a control system based onthe use of a digital computer, as in the example described in thepreviously cited Manual 555. However, it is to be understood that thebasic method of operation described hereinafter may be applied at anyrailroad track switch location where control apparatus is availablehaving the capability of performing the functions and storinginformation discussed hereinafter. More specifically, in practicing ourinvention, the speed of each cut of cars traversing a track switch ismeasured at that point. In the specific showing herein, this speedmeasurement is accomplished by determining the time of passage at apoint adjacent the track switch between the first and last axle of thecut of cars. In the automatic control system assumed, the length betweenthese axles has already been recorded and is stored in the controlcomputer. Thus the speed may be computed by dividing the distancebetween the axles by the time elapsed between the passage of theselected axles. Following this speed measurement, the existence of apotential cornering situation is determined by checking the nextapproaching cut of cars for a higher speed and a requirement for adiverging route at that switch. These facts are already stored in thecontrol computer storage banks due to previous operations in controllingthe approaching cut of cars this far along its selected route. A timeinterval is then computed as a product of the difference between thereciprocals of the speeds of the two successive cuts of cars and apreselected clearance distance along each diverging track beyond thatswitch. The latest available speed information stored in the computerfor the following cut is used while the just measured speed for theleading cut of cars as it passed over that switch is available. Apreselected distance to clearance for each switch in the yard is alsostored in the computer. This distance to points along the divergingtracks beyond the switch is selected such that any combination ofconfigurations of two cars will clear at that point, that is, nocornering will occur. This computed time interval is applied as a delaytime prior to the delivery of the next position control to this switchmovement, that is, the position control for establishing the route forthe following cut. The computation formula is developed, as will beexplained later, so that if the switch could be changed and thefollowing cut arrives within the switch detector section prior to theexpiration of this time period, there is a very high degree ofprobability that cornering will occur. However, when the positioncontrol is delivered with the following out within the detector section,the switch is locked so that no movement can occur and the divergingroute is not established. Of course the following cut is misrouted and acatch up with the preceding cut may occur within a relatively shortdistance, but the more serious situation of the cornering accident isavoided. If the following out has not reached the detector section,prior to the expiration of the time delay, the position controldelivered to the switch movement is executed and the diverging route isestablished, since cornering can not now occur.

We shall now describe the arrangement of our invention in greater detailreferring from time to time to the accompanying drawings in which:

FIG. 1 is a schematic illustration of two single cars moving over aswitch showing the various distances and factors used to derive theanti-cornering equations.

FIG. 2 is a diagrammatic illustration of a portion of a railroadclassification yard to which our invention is applied.

Where appropriate, similar reference characters have been used in eachof the drawing figures to designate similar elements of theillustrations.

Referring now to FIG. 1, there is shown, by conventional single linerepresentation, a stretch of railroad track extending from the left ofthe drawing through the marked points A, B, C, D, and F. This stretch oftrack includes a typical track switch, designated W, which at times maybe positioned to divert cars to the track stretch through points E andG. Point C is specifically located a few feet in the approach to thepoints of track switch W. A wheel detector device or the equivalentapparatus is associated with point C to provide the means to sense whenan axle of a moving car is located at that point. Such method ofdetecting the axles of moving cars is conventional and the details neednot be shown.

Points B, D, and E define the boundaries of the locking area for thetrack switch, more commonly known as the switch detector section. Aconventional track. circuit or other well known means is provided todetect the presence of one or more axles 'within this switch detectorsection and, under such situation, to prevent the switch controlcircuits from responding to any positioning control that might besupplied in an attempt to make the swtch change position. These pointsare so located as to insure that the switch can not change position whenany car is passing over it. Of course, the nearest to this switch thatthe first axle of any approaching car can be located and still have theswitch change position to establish a route for that car is point B.

Points F and G are defined as the clearance points for the track switch.Said in another way, when a car is routed toward point P, its last axlemust advance at least as far as point P to assure it will not becornered by a following car routed towards point G. Similarly, when acar is routed toward point G, its last axle must reach that point inorder to insure against a similar cornering by a car moving along thetrack towards F. The location of points F and G are determined whensetting up the yard control system by taking into account trackcurvatures and the worse case car body geometries to be ex pected. Withpoints F and G defined in this way, track sections CF and CG are notnecessarily equal in length. However, for purposes of the anti-corneringarrangement provided by our invention, their lengths are set equal tothe greater of the two. Such clearance distances for each switch in theclassification yard will be predetermined and stored within the controlcomputer.

Point A is not a specifically fixed location but is rather defined asthe location of the first axle of a following car, such as car 2, whenthe last axle of the leading car, such as car 1, is located at point C.Since the location of point A thus depends upon the spacing betweencars, it is obviously a variable. If the car spacing is such that pointA falls within the switch locking area, that is, within the bounds ofpoints B, D, and E, cornering obviously can not take place since theswitch is locked. Therefore for purposes of the anti-corneringcomputations involved in the arrangement of our invention, point A isconstrained to be at, or in the approach to, point B.

Two single car cuts are shown moving along the stretch of railroadtrack, each represented in schematic form as a 4-axle car. However, aswill become apparent, anti-cornering protection for 6- or S-axle carswill be provided in a similar manner. The symbols L and L are defined asthe wheel bases, that is, the distance from the first axle to the lastaxle for cars 1 and 2, respectively. For multi-car cuts, the distance Lis also measured from the first axle, of the first car, to the lastaxle, of the last car. The symbols O and 0 are, respectively, theoverhangs for cars 1 and 2, that is, the distance at each end of the carfrom the end of the car body to the center of the first axle at thatend. These lengths, or distances 0, may or may not include the length ofthe coupler at the end of the car. However, as will become apparentlater, this is unim portant to the arrangement of our invention sincethese distances cancel out of the equations used. The length L for eachcar or cut of cars will be stored within the control computer, havingbeen determined during the measurement of the parameters of each car orcut of cars moving throughoutthe yard. One arrangement for making thesemeasurements is described and shown: in a copending application for-Letters Patent of the US. Ser. No. 712,738, filed Mar. 13, 1968 e by E.F. Brinker for the Measurement of Freight'Car Parameters, whichapplication has the same assignee as this present application. Alsoshown, associated with each of the schematic illustrations for themoving cars, are-velocity arrows designated V and V These symbolsdesignate the velocities of the respective-cars and are assumed forpractical purposes to remain constant as the cars move through the areaof interest in the direction shown.

With car 1 in FIG. 1 routed towards point P as illus trated, we shallassume that the proper preselected rout-' ing for car 2 is towards pointG. Cornering between these two cars will then occur if the switch canchange, position and car 2 can overtake car 1 before the last axle ofcar 1 reaches point F. But this overtaking condition can exist only ifthe following inequality is true:

where:

S length of track section AB S --length of track section BC S length oftrack section CF S length of track section CG V V 0 and O- -aspreviously defined.

Since the quantity [S --(O is approximately equal to zero and is anywayvery much less than S expression (1) may be simplified to the following:

g an-l-Sco V V (2) By rearranging expression (2), we obtain:

@ fiupi If car 1 is routed toward point G and the proper routing for car2 is toward point P, an expression for the overtake condition can bedeveloped in a manner similar to the development of expression (3),resulting in:

V2 1 2 Since S and S are equal by definition, expressions (3) and (4)are identical. By substituting S for S and S a general expression thatapplies to both of the two overtake conditions is obtained:

SAB 1 1 v2 v2) (5) Both the left-hand and right-hand sides of inequality(5) dimensionally represent time, since each is distance divided byvelocity.

Expression (5) provides the basis for our anti-cornering protectionarrangement. This basis may be stated to be that potential corneringsituations will be prevented if the track switch can not change positionwhen this inequality is satisfied by existing car spacings andvelocities. This can be accomplished by imposing a time constraint onthe control of the switch. Thus a time interval of delay, prior topositioning the switch to establish the diverging route for thefollowing car, must normally be provided, i.e., computed, when each cartraverses the switch. Said in another way, as long as the time for thefollowing car to reach the detector section, i.e., arrive at point B,which time is represented by the left quantity of expression (5),remains less than the catchup time beyond the switch, as represented bythe right quantity, cornering will occur if the switch is allowed tochange position to establish a diverging route for the following car.Conversely, if car spacings and velocities are such that the time priorto arrival at point B for the following car, i.e., the left quantity, isequal to or greater than the catch-up time of the right quantity,cornering will not occur even if the switch changes position. Therefore,if, subsequent to the time that the last axle of car 1 is located atpoint C, the command for the switch to change position is not deliveredto the switch control circuits until a time interval has elapsed that isequal to or greater than the catch-up time represented by the rightquantity of expression (5 any potential cornering will be prevented.

For computation purposes, the left quantity of the inequality (5) is nota readily usable item, from a practical standpoint, since, by thedefinition of point A, the distance S is a relatively unmeasurablevariable for each car. However, the right quantity contains only termswhich may be measured for each car or for which information ispredetermined and thus available. Thus, this delay time interval foreach car traversing the switch may be represented by the right quantityof expression (5) and can be expressed by the following equation:

Tzs (6) This means that, when the car spacing and car velocities aresuch that cornering can occur, i.e., inequality (5) is satisfied, theswitch will not be commanded to change position until the first axle ofcar 2 has passed point B. Such being the case, the switch cannot changeposition and cornering will be prevented. If car spacing and velocitiesare such that cornering cannot occur, i.e., inequality (5) is notsatisfied, time Twill elapse before the first axle of car 2 has passedpoint B. Under this condition, when the switch command is delivered, theswitch will change position to properly route car 2. It is obvious thatonly positive values of T (when V is greater than V are used to imposetime constraints on control of the switch. The basic anti-corneringarrangement described above may be applied at every switch location in aclassification yard. Referring to FIG. 2, we shall describe the generaldetails of such an application and also in a general way the operationthereof. FIG. 2 is a diagrammatic illustration of an anti-corneringsystem in a classification yard using a flow chart and conventionalblock diagram format to represent the apparatus and its operation. Thesingle line representation at the top of FIG. 2 illustrates part of thetrack layout in a classification yard. In the portion illustrated, cutsof cars moving from the crest of the hump at the left of the drawingtravel through the master retarder, over switch W through the groupretarder for one group of storage tracks, and over at least switch W tothe preselected one of that group of storage tracks, here designated astracks 8 to 14. Switch W designates a track switch which routes carsover one diverging track to storage tracks 1-7 and by the otherdiverging movement to the previously mentioned storage tracks 8-14.Switch W is the initial group switch for routing the cuts of cars to thevarious tracks of the illustrated storage group. Other switchesassociated with storage track group 844 are not specifically designatedbut similar control arrangements including the anti-cornering protectionat provided for each of these switches.

This particular classification yard is provided with an automaticsystemof operation, controlled by a digital computer shown by aconventional block at the bottom of FIG. 2. Various forms of digitalcomputers may be adapted and applied to control such automaticclassification yard systems. A specific example of one such computerunit actually used in an automatic yard control system, which furtherincludes the anti-cornering arrangement disclosed herein, is theHoneywell Model DDP-516, manufactured by the Computer Control Divisionof Honeywell, Inc., located in Framingham, Mass. The interfacing of thecomputer with the other yard apparatus, and its programming to executethe control functions required, are not a part of the inventive conceptherein disclosed. Thus it is sufiicient to define that this computerreceives the routing information for the cuts of cars, issues switchcontrols to properly establish the desired routes to the preselectedstorage tracks, receives car and track characteristics and conditionmeasurements from the track side apparatus, computes the desired leavingspeed from the various retarders, issues controls to these retarders foroperation to obtain the selected speeds, and receives car speedinformation measured at various points as cuts of cars move throughoutthe yard to the selected storage tracks. The computer records and/orstores the information and measurements for later use as needed in theoperation of the control system. A specific arrangement is described inthe previously cited Manual 555. In addition to car speed information,the stored information includes car lengths and other related parametersfor the various cuts of cars moving in the yard, as described, forexample, in the aforementioned Brinker application, and thepredetermined clearance distance for each switch.

The flow chart arrows shown in FIG. 2 indicate in some greater detailthe information received and the controls issued, both of which arerecorded, which are particularly involved in the anti-corneringarrangement of our invention. For example, a desired leaving speed iscomputed for the master retarder and for a group retarder for each cutof cars. These are indicated by the flow lines designated by symbol Vwith a prefix M or G designating the master or group retarder. Theactual exit speed from the retarders for each cut of cars is measured bythe associated radar apparatus, conventionally shown,

which is provided with a velocity meter so that direct speed informationis supplied to the computer, as designated by the flow lines V Both theV and V speed information for each cut of cars as it passes through themaster and group retarders is stored by the computer. It is to be notedthat the distance between the end axles, that is, the lead axle and thefinal axle of each cut of cars, is also stored within the computer. Thisdistance is measured during the approach to the master retarder, asdescribed in the aforementioned Brinker application, and is supplied tothe computer as indicated by the flow line designated by the previouslydefined symbol L. As each cut of cars traverses a switch location, itspresent speed is measured in a manner previously described briefly andin more detail shortly. This information is supplied to the computer forstorage as illustrated by the flow lines designated by symbol V with aprefix in accordance with the associated switch location.

The remaining flow lines, designated by the symbol WP with a subscriptto designate the particular associated switch, represent the positioningcontrols supplied from the computer to the switch movements in order toestablish the preselected routes for the cuts of cars. The necessaryinputs, outputs, and stored programs are provided within the computer sothat the car following action and the issuance of the necessary switchcontrol at the proper times are performed by the computer. However, theswitch locking constraints upon the operation of the switch movements isprovided within the switch detector sections and associated waysideapparatus and not within the computer. In other words, the computercontrols the positioning of the track switches only to the extent thatit delivers positioning commands to the external switch control andlocking circuits. These external control and locking circuits providethe necessary safety so that switch points are not moved while cuts ofcars are passing over them, or are within such a short range of approachthat the full movement of the switch points cannot be completed beforethe arrival of the lead wheels of the car. Such safety controls areconventional in the automatic operation of switch movements and need notbe further described.

It is now assumed that two cuts of cars are approaching switch W thesecuts having moved along the selected routes from the hump through themaster retarder, switch W and the selected group retarder towards switchW The final speed control function for each cut is performed as itpasses through the group retarder. The various items of speedinformation have been recorded for each of these cuts and stored in thedigital computer. For exam ple, for each cut, speed informationdesignated by the flow lines MV MV W V GV and GV has, or shortly willhave, been taken and recorded by the computer. During the approach ofeach of these two cuts to the master retarder, car and/ or cutparameters were measured and recorded so that at this time a wheel basedistance L is stored in the computer for each cut of cars. The carfollowing action by the control system as these cuts moved throughoutthe yard from section to section, as detected by wheel detectors, trackcircuits, and/or other conventional means, results in the location ofeach cut and its identity being known. Thus its recorded informationregarding speed and characteristic distances is available wheneverdesired. In other words, the digital computer, through its car followingprocedures, recognizes which particular cuts are now approaching switchW and can identify and recall the stored information concerning theindividual cuts.

As the first or leading cut passes point C in the immediate approach toswitch W its Velocity vV is measured. One specific way of accomplishingthis is to determine the time elapsing between the passage of the firstand last axles of this particular cut, as detected by the wheel detectorat point C. This timing may be accomplished by recording exact timesbased on a standard clock or by recording a count of uniform clockpulses provided within the computer apparatus. In any event, thevelocity V is then determined in accordance with the wheel base Ldivided by the elapsed time.

When the last axle of this lead cut is detected as passing point C inthe approach to switch W the computer determines whether or not apotential cornering situation exists at the present time. This isaccomplished by seeking the answers to three questions. First, is thereanother cut approaching the switch in question, i.e., switch W If theanswer to this first question is yes, then a second question is asked:Does the position of the switch have to be changed to properly route theapproaching second cut? If the answer to this second question is alsoyes, then a third question is asked: Is the current velocity (V of theapproaching second cut greater than the just determined velocity V ofthis lead cut? If the answer to this third question is also yes, apotential cornering situation exists. Obviously, if the answer to anyone of these questions is no, there is no potential cornering situationexisting and further action is not required for this particular cut.These three questions are all answered within the computer by referenceto information already stored. This includes the current locations ofthe assumed cuts of cars, the stored routes, and the speed informationrecorded for the various cuts. It is to be noted that V used for thesecond cut, in determining whether it is moving faster, is the latestinformation available regarding that particular cut. In the situationhere assumed, this would likely be either the computed leaving speeddesired from the group retarder, designated by VG or the actual exitspeed from the group retarder, as measured by the radar apparatus anddesignated as GV If, however, the next cut to follow this same routetowards switch W is even further back up the hump, the V informationused will be that concerning its operation in the master retarder orperhaps that measured at the lead switch group W When a potentialcornering situation exists, the delay time interval for switch operationis then computed in accordance with expression (6) previously discussed.All the information necessary for solving this equation is stored withinthe computer at this time. The predetermined clearance distances S arestored for each of the switches in the yard and thus are available forswitch W Measurement of V of the leading cut has just been completed asit passed point C while the velocity V of the following cut is storedand the latest available information again is used for this particularitem.

When the delay time has been computed, one possible method forcontrolling and providing the anti-cornering protection is to withholdthe switch position or control commands designated by the flow line WgPfor the following cut of cars until the time delay has elapsed. Thisdelay time designated by the arrow symbol T within the computer block ismeasured from the time of the passage of the last axle of the first cutat point C. The operation is illustrated conventionally in FIG. 2 by theswitch control delay block within the computer to which is applied thetime delay signal T Several methods by which the application of theswitch control may be delayed will be apparent to those skilled in thecomputer art. For exam ple, a gating circuit may be used which will passthe switch control only when the time signal expires. Or some form ofbinary variable may be supplied which is changed to its permissivecondition when the particular time is reached, on the computer clock, atwhich the delay time has expired.

Whatever the method, when time T expires, the switch command forpositioning the switch to establish the route for the following cut willbe supplied to the switch movement and locking apparatus at the'switchlocation. Referring to FIG. 1, if the leading axle of this following cut2 has not reached point B in the approach to switch W when the switchposition command is supplied, sufficient time is available and theswitch movement will respond to the command to position the switch forthe diverging route for the second cut. However, if the leading axle ofcut 2 has entered the switch detector section, bounded by points B, D,and E, switch W is locked in its existing position and no movement ofthe switch points can occur. Under this condition, cut 2 will follow theroute already established for out 1 even though the preselected routecalls for a diverging movement. This misrouting of cut 2 and itsprobable catch up with cut 1 is, however, more acceptable than acornering accident which was highly probable under these conditions. Aspreviously mentioned, catch up between two cuts moving along the sametrack is the equivalent to coupling within the storage tracks and nodamage is expected to result to the cars or their contents. It is truethat this misrouting requires a trimming operation which will result inlost time in the overall yard operation, but this normally is less losttime than a cornering accident will cause through blocking a portion ofthe yard. With the provision of misrouting reports from the digitalcomputer which records the various misroutes, a misrouted car and itslocation are identified and the car can be easily recovered and moved toits proper position in the classification yard.

The described arrangement of our invention thus provides a practical andefficient anti-cornering system for use in classification yards.Misroutings of cuts of cars occur only to avoid anti-cornering accidentsand are-thus acceptable minimum delays in line with the goal ofincreasing the safety and efliciency of yard operations. Most of thefunctions required to provide our anti-cornering system are already usedin the yard and the information or data thus already available withinthe computer control apparatus. Even the wheel detector at point C inthe immediate approach of each switch is used also in the car-followingoperation throughout the yard. Some additional storage elements withinthe computer and additional programming of the computer operationconstitute most of the additional apparatus or operation required toprovide this anti-cornering arrangement. The humping speed need not bereduced in order to space the cars to prevent cornering and thus thefull capacity of the yard may be used. Also, the switch detectorsections need only be of sufiicient length, whether they be trackcircuits or other means, to assure that switch points will be fullypositioned prior to the arrival of the leading wheel of any cut and thatno switch movement will occur while the cut of cars is passing over thatswitch.

Having thus described our invention, what we claim is:

1. A method for preventing cornering between successive cuts of railroadcars traversing a track switch, said switch being included in a detectorlocking section to prevent movement of the switch while a cut istraversing said section, comprising the steps of,

(a) measuring the speed of the first of the two successive cuts whilesaid first cut traverses said switch in its first position,

(b) measuring the speed of the second cut of said successive cuts whileapproaching said switch,

(c) computing, by a programmed computer, in accordance with the measuredspeeds and a known distance to the clearance point between cuts movingalong the diverging routes beyond said switch, the time intervalrequired prior to arrival of said second cut at said switch to insureclearance of said first car at said point when said second car travelsthe diverging route, and

(d) delaying the positioning of said switch to the opposite position toroute said second cut until the expiration of said time interval.

2. The method for preventing cornering as defined in claim 1 in whichsaid time interval is computed by said computer as the product of saiddistance to the clearance point and the difference between thereciprocals of the measured speeds of said successive cuts, where thespeed of said second cut is greater.

3. The method of preventing cornering as defined in claim 2, where saidswitch is located in a railroad classification yard operated by anautomatic control system, and in which,

-(a) the step of measuring the speed of said first cut includes,

(1) measuring the time for passage of a selected portion of said firstcut at a point adjacent said switch, the length of said selected portionbeing known and recorded in said control system,

(2) calculating by said computer the speed in accordance with saidrecorded length and said measured time, and

(b) the step of measuring the approach speed of said second cut is partof the control operations of said yard, the latest valid speedinformation recorded in said control system being used.

4. The method of preventing cornering as defined in claim 3 where saidautomatic yard control system includes a digital computer for recordingand storing length, speed, and route information for each cut andclearance distance for each switch and for computing said time interval,and in which,

(a) the step of delaying comprises delaying the delivery from saidcomputer to the switch of the switch position control for said secondcut until the expiration of said time interval,

and which further includes the step of,

(b) determining in said computer from the stored data that a potentialcornering situation exists prior to computing and enforcing said timeinterval delay.

5. Apparatus for controlling the operation of a track switch movement,which positions an associated switch located in a stretch of track to afirst or second position to establish a selected one of two divergingroutes for cuts of railroad cars traversing the switch, comprising incombination,

(a) a first means responsive to the movement of a cut of cars over saidswitch for measuring the speed of that cut,

(b) a second means responsive at selected points to the approach of thenext following cut of cars for determining the present speed of approachof that following cut,

(c) a computing means controlled by said first and second means, whensuccessive cuts are traversing and approaching said switch,respectively, for computing a time interval in accordance with apredetermined relationship between the difference between the speeds ofthe two successive cuts and a preselected distance from said switch toclearance points along each diverging route within which distance cutssimultaneously moving along said diverging routes will corner, and

(d) delay means with connections to said switch movement and controlledby said computing means for delaying the operation of said movement toposition said switch to establish a diverging route for said followingcut until the expiration of said time interval.

6. Control apparatus as defined in claim 5 further including,

(a) a detector track section spanning said switch location, and

(b) detection means responsive to a cut of cars occupying said detectorsection and having connections for locking said switch in its existingposition when a cut of cars is detected, whereby said switch is retainedin the position existing for the leading cut when said following cutoccupies said detector section prior to the expiration of said timeinterval.

7. Control apparatus as defined in claim 6, the combination furtherincluding,

(a) means responsive to the passage of each cut of cars 11 at a point inapproach to said switch for measuring the length of a preselected partof that cut, and

(b) said first means comprising,

(1) timing means responsive to the passage of a cut of cars over saidswitch for measuring the time for passage of said preselected part ofthat cut,

(2) speed computing means controlled by said length measuring means andby said timing means for determining the speed of each cut moving oversaid switch in accordance with the measured length and time of passageof said pre-selected part of each cut.

8. Control apparatus as defined in claim 7, in which said delay meanscomprises,

(a) a delay element operable to a first and a second condition andhaving connections to said switch movement for inhibiting the deliveryof control functions thereto only when said delay element is in itsfirst condition,

(b) said delay element being controlled by said computing means foroperating to said first condition during said time interval and forholding in said second condition at all other times.

9. Control apparatus for a track switch in a railroad classificationyard selectively connecting a first stretch of track to second and thirddiverging track stretches, comprising in combination,

'(a) operating means for said switch for moving it between a first and asecond position to selectively route cuts of cars to said second andsaid third track stretches respectively,

(b) a first speed measuring means for measuring the speed of a cut ofcars as it traverses said switch,

(0) a second speed measuring means for measuring the speed of a cut ofcars approaching said switch, and

(d) delay means controlled by said first and second speed measuringmeans, in accordance with a pre- 12 determined relationship between themeasured speeds of two successive cuts of cars and a preselectedclearance distance along said second and third track stretches, andhaving connections to said operating means for delaying operation ofsaid switch to its other position between successive cuts of cars routedover said switch to diverging tracks when the following cut will catchup to the leading cut within said preselected distance, thereby avoidingcornering of the lead out by the following cut. 10. Switch controlapparatus as defined in claim 9, further including,

(a) computing means with connections for receiving speed measurementsfrom said first and said second speed measuring means and having storedtherein said preselected distance,

(1) said computing means being responsive to the reception of a speedmeasurement of said leading cut, when the measured speed of saidfollowing cut routed to the diverging track is greater, for computing atime interval in accordance with said predetermined relationship,

(b) said delay means being controlled by said computing means fordelaying the movement of said switch to its other position after passageof said lead cut, to route said following cut to the diverging route,until the end of said time interval.

References Cited UNITED STATES PATENTS 2,880,308 3/1959 Tsiang 246-161ARTHUR L. LA POINT, Primary Examiner G. H. LIBMAN, Assistant ExaminerUS. Cl. X.R. l0426

